Method and apparatus for determining consumable lifetime

ABSTRACT

A plasma processing device comprising a gas injection system is described, wherein the gas injection system comprises a gas injection assembly body, a consumable gas inject plate coupled to the gas injection assembly body, and a pressure sensor coupled to a gas injection plenum formed by the gas injection system body and the consumable gas inject plate. The gas injection system is configured to receive a process gas from at least one mass flow controller and distribute the process gas to the processing region within the plasma processing device, and the pressure sensor is configured to measure a gas injection pressure within the gas injection plenum. A controller, coupled to the pressure sensor, is configured to receive a signal from the pressure sensor and to determine a state of the consumable gas inject plate based upon the signal. A method of determining the state of the consumable gas inject plate comprises: measuring a change in the gas injection pressure associated with either a change in the process gas mass flow rate or the processing pressure; determining a response time for the change in pressure; and comparing the response time during erosion to a response time during no erosion.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and is related to U.S.Provisional Application Serial No. 60/434,657, filed on Dec. 20, 2002.The entire content of this application is incorporated herein byreference.

FIELD OF THE INVENTION

[0002] The present invention relates to a method and apparatus fordetermining consumable lifetime in an erosive environment, and moreparticularly to a method and apparatus for determining the lifetime of aconsumable gas injection component.

BACKGROUND OF THE INVENTION

[0003] In semiconductor manufacturing, plasma is often employed tocreate and assist surface chemistry within a plasma reactor necessary toremove material from and deposit material to a substrate. In general,plasma is formed within the plasma reactor under vacuum conditions byheating electrons to energies sufficient to sustain ionizing collisionswith a supplied process gas. Moreover, the heated electrons can haveenergy sufficient to sustain dissociative collisions and, therefore, aspecific set of gases under predetermined conditions (e.g., chamberpressure, gas flow rate, etc.) are chosen to produce a population ofcharged species and chemically reactive species suitable to theparticular process being performed within the chamber (e.g., etchingprocesses where materials are removed from the substrate or depositionprocesses where materials are added to the substrate). One pre-requisiteto ensuring a uniform process includes a uniform injection of processgas to the plasma chemistry above the substrate. FIG. 1 presents ashowerhead-type gas injection system 1 comprising a gas injectionassembly body 10, a gas inject plate 12, and optionally one or morebaffle plates 14 installed within gas injection plenum 16. In general,the gas injection assembly body 10, the gas inject plate 12, and the oneor more baffle plates are fabricated from aluminum. The process gas canbe supplied to the gas injection plenum 16 via a mass flow controller 30and/or pressure regulator 32 In order to minimize the damage sustainedby exposure to the processing plasma, a consumable or replaceablecomponent can be inserted within the processing chamber to protect thesurfaces of more valuable components that would impose greater costsduring frequent replacement. Therefore, the gas injection system 1depicted in FIG. 1 can further comprise a consumable gas inject plate20. The consumable gas inject plate 20 can be fabricated from materialssuch as silicon, quartz, sapphire, alumina, carbon, silicon carbide,etc. In general, it is desirable to select surface materials that duringerosion minimize the introduction of unwanted contaminants, impurities,etc. to the processing plasma and possibly to the devices formed on thesubstrate. As a result of their consumable nature, the erosion ofexposed components in the plasma processing system can lead to a gradualdegradation of the plasma processing performance and ultimately tocomplete failure of the system. Therefore, it is important to properlymaintain these components. For instance, these consumables orreplaceable components are typically considered as part of a process kitthat is frequently maintained during system cleaning. In manufacturingenvironments, consumable components, such as the consumable gas injectplate 20, are replaced during pre-determined maintenance intervals,which are often dictated by a measure of usage such as the number of RFhours. Since the measure of usage is determined conservatively,consumable components can be replaced before the end of their lifetime,hence, leading to increased manufacturing costs, downtime, etc.

SUMMARY OF THE INVENTION

[0004] A method and apparatus are described for determining consumablelifetime, and particularly a method and apparatus for determining alifetime of a consumable gas injection component.

[0005] More particularly, a gas injection system in a plasma processingdevice is described comprising: a gas injection assembly body configuredto receive a process gas from one or more mass flow controllers; aconsumable gas inject plate coupled to the gas injection assembly body,the consumable gas inject plate comprising one or more orifices todistribute the process gas to the plasma processing device; a pressuresensor coupled to the gas injection assembly body and configured tomeasure a gas injection pressure within a gas injection plenum formed bythe gas injection assembly body and the consumable gas inject plate; anda controller coupled to the pressure sensor and configured to determinea state of the consumable gas inject plate from a change in the gasinjection pressure.

[0006] Additionally, a method of determining the state of a gasinjection system in a plasma processing device comprises: changing aprocess parameter in the plasma processing device to affect a change ofa gas injection pressure in the gas injection; measuring a response timecorresponding to a change of the gas injection pressure using thepressure sensor, wherein the response time corresponds to a first timeduration when the consumable gas inject plate has not been eroded andthe response time corresponds to a second time duration when theconsumable gas inject plate has been eroded; and comparing the responsetime to at least one of the first and second time durations in order todetermine the state of the gas injection system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] These and other advantages of the invention will become moreapparent and more readily appreciated from the following detaileddescription of the exemplary embodiments of the invention taken inconjunction with the accompanying drawings, where:

[0008]FIG. 1 shows a schematic representation of a typical gas injectionsystem for a plasma processing device;

[0009]FIG. 2 shows a block diagram of a plasma processing device inaccordance with an embodiment of the present invention;

[0010]FIG. 3 shows a block diagram of a plasma processing device inaccordance with another embodiment of the present invention;

[0011]FIG. 4 shows a block diagram of a plasma processing device inaccordance with another embodiment of the present invention;

[0012]FIG. 5 shows a block diagram of a plasma processing device inaccordance with another embodiment of the present invention;

[0013]FIG. 6 shows a block diagram of a plasma processing device inaccordance with another embodiment of the present invention;

[0014]FIG. 7A shows a schematic representation of a gas injection systemfor a plasma processing device in accordance with another embodiment ofthe present invention;

[0015]FIG. 7B shows a schematic representation of a gas injection systemfor a plasma processing device in accordance with another embodiment ofthe present invention;

[0016]FIGS. 8A and 8B show simplified schematic diagrams of a non-erodedand an eroded orifice, respectively, in a gas injection system inaccordance with another embodiment of the present invention;

[0017]FIG. 8C shows a schematic diagram of a response curve for ameasurement system coupled to a gas injection system in accordance withan embodiment of the present invention;

[0018]FIG. 9A shows another schematic representation of a gas injectionsystem for a plasma processing device in accordance with an embodimentof the present invention;

[0019]FIG. 9B shows another schematic representation of a gas injectionsystem for a plasma processing device in accordance with an embodimentof the present invention; and

[0020]FIG. 10 presents a method of determining a consumable lifetime fora gas injection component in accordance with an embodiment of thepresent invention.

DETAILED DESCRIPTION OF AN EMBODIMENT

[0021] A plasma processing device 100 is depicted in FIG. 2 comprising aplasma processing chamber 110, a gas injection system 101 coupled to theplasma processing chamber 110, a diagnostic system 112 coupled to thegas injection system 101 of the plasma processing chamber 110, and acontroller 114 coupled to the diagnostic system 112 and the plasmaprocessing chamber 110. The controller 114 is configured to receive oneor more signals from the diagnostic system 112, process the one or moresignals, and determine a status of the gas injection system 101 and itsconsumable components. In the illustrated embodiment, plasma processingdevice 100, depicted in FIG. 2, utilizes a plasma for materialprocessing. Desirably, plasma processing device 100 comprises an etchchamber.

[0022] According to the illustrated embodiment depicted in FIG. 3,plasma processing device 100 can comprise plasma processing chamber 110,gas injection system 101, substrate holder 120, upon which a substrate125 to be processed is affixed, and vacuum pumping system 130. Substrate125 can be, for example, a semiconductor substrate, a wafer or a liquidcrystal display. Plasma processing chamber 110 can be, for example,configured to facilitate the generation of plasma in processing region115 adjacent a surface of substrate 125. An ionizable gas or mixture ofgases is introduced via gas injection system 101 and the processpressure is adjusted. Additionally, a control mechanism (not shown) canbe used to throttle the vacuum pumping system 130. Desirably, plasma isutilized to create materials specific to a pre-determined materialsprocess, and/or to aid the removal of material from the exposed surfacesof substrate 125. The plasma processing device 100 can be configured toprocess 200 mm substrates, 300 mm substrates, or larger.

[0023] Substrate 125 can be, for example, affixed to the substrateholder 120 via an electrostatic clamping system. Furthermore, substrateholder 120 can, for example, further include a cooling system includinga re-circulating coolant flow that receives heat from substrate holder120 and transfers heat to a heat exchanger system (not shown), or whenheating, transfers heat from the heat exchanger system. Moreover, gascan, for example, be delivered to the back-side of substrate 125 via abackside gas system to improve the gas-gap thermal conductance betweensubstrate 125 and substrate holder 120. Such a system can be utilizedwhen temperature control of the substrate is required at elevated orreduced temperatures. For example, the backside gas system can comprisea two-zone gas distribution system, wherein the helium gas gap pressurecan be independently varied between the center and the edge of substrate125. In other embodiments, heating/cooling elements, such as resistiveheating elements, or thermo-electric heaters/coolers can be included inthe substrate holder 120, as well as the chamber wall of the plasmaprocessing chamber 110 and any other component within the plasmaprocessing device 100.

[0024] In the illustrated embodiment, shown in FIG. 3, substrate holder120 can comprise an electrode through which RF power is coupled to theprocessing plasma in process space 115. For example, substrate holder120 can be electrically biased at a RF voltage via the transmission ofRF power from a RF generator 140 through an impedance match network 150to substrate holder 120. The RF bias can serve to heat electrons to formand maintain plasma. In this configuration, the system can operate as areactive ion etch (RIE) reactor, wherein the chamber and upper gasinjection electrode serve as ground surfaces. A typical frequency forthe RF bias can range from 0.1 MHz to 100 MHz. RF systems for plasmaprocessing are well known to those skilled in the art.

[0025] Alternately, RF power is applied to the substrate holderelectrode at multiple frequencies. Furthermore, impedance match network150 serves to maximize the transfer of RF power to plasma in plasmaprocessing chamber 110 by minimizing the reflected power. Match networktopologies (e.g. L-type, π-type, T-type, etc.) and automatic controlmethods are well known to those skilled in the art.

[0026] Vacuum pump system 130 can, for example, include aturbo-molecular vacuum pump (TMP) capable of a pumping speed up to 5000liters per second (and greater) and a gate valve for throttling thechamber pressure. In conventional plasma processing devices utilized fordry plasma etch, a 1000 to 3000 liter per second TMP is generallyemployed. TMPs are useful for low pressure processing, typically lessthan 50 mTorr. At higher pressures, the TMP pumping speed falls offdramatically. For high pressure processing (i.e., greater than 100mTorr), a mechanical booster pump and dry roughing pump can be used.Furthermore, a device for monitoring chamber pressure (not shown) can becoupled to the plasma processing chamber 110. The pressure measuringdevice can be, for example, a Type 628B Baratron absolute capacitancemanometer commercially available from MKS Instruments, Inc. (Andover,Mass.).

[0027] Controller 114 comprises a microprocessor, memory, and a digitalI/O port capable of generating control voltages sufficient tocommunicate and activate inputs to plasma processing device 100 as wellas monitor outputs from plasma processing device 100. Moreover,controller 114 can be coupled to and can exchange information with RFgenerator 140, impedance match network 150, the gas injection system101, diagnostic system 112, vacuum pump system 130, as well as thebackside gas delivery system (not shown), the substrate/substrate holdertemperature measurement system (not shown), and the electrostaticclamping system (not shown). For example, a program stored in the memorycan be utilized to activate the inputs to the aforementioned componentsof plasma processing device 100 according to a process. In addition,controller 114 can be configured to receive one or more signals from thediagnostic system 112, process the one or more signals, and determine astate of the gas injection system 101 and its consumable components. Oneexample of controller 114 is a DELL PRECISION WORKSTATION 610™,available from Dell Corporation, Austin, Tex.

[0028] In the illustrated embodiment, shown in FIG. 4, the plasmaprocessing device 100 can, for example, further comprise either astationary, or mechanically or electrically rotating magnetic fieldsystem 160, in order to potentially increase plasma density and/orimprove plasma processing uniformity, in addition to those componentsdescribed with reference to FIG. 2 and FIG. 3. Moreover, controller 114can be coupled to magnetic field system 160 in order to regulate thespeed of rotation and field strength. The design and implementation of arotating magnetic field is well known to those skilled in the art.

[0029] In the illustrated embodiment, shown in FIG. 5, the plasmaprocessing device 100 of FIG. 2 and FIG. 3 can, for example, furthercomprise an upper electrode 170 to which RF power can be coupled from RFgenerator 172 through impedance match network 174. A typical frequencyfor the application of RF power to the upper electrode can range from0.1 MHz to 200 MHz. Additionally, a typical frequency for theapplication of power to the lower electrode can range from 0.1 MHz to100 MHz. Moreover, controller 114 is coupled to RF generator 172 andimpedance match network 174 in order to control the application of RFpower to upper electrode 170. The design and implementation of an upperelectrode is well known to those skilled in the art.

[0030] In the illustrated embodiment, shown in FIG. 6, the plasmaprocessing system of FIG. 3 can, for example, further comprise aninductive coil 180 to which RF power is coupled via RF generator 182through impedance match network 184. RF power is inductively coupledfrom inductive coil 180 through dielectric window (not shown) to plasmaprocessing region 115. A typical frequency for the application of RFpower to the inductive coil 180 can range from 10 MHz to 100 MHz.Similarly, a typical frequency for the application of power to the chuckelectrode can range from 0.1 MHz to 100 MHz. In addition, a slottedFaraday shield (not shown) can be employed to reduce capacitive couplingbetween the inductive coil 180 and plasma. Moreover, controller 114 iscoupled to RF generator 182 and impedance match network 184 in order tocontrol the application of power to inductive coil 180. In an alternateembodiment, inductive coil 180 can be a “spiral” coil or “pancake” coilin communication with the plasma processing region 115 from above as ina transformer coupled plasma (TCP) reactor. The design andimplementation of an inductively coupled plasma (ICP) source, ortransformer coupled plasma (TCP) source, is well known to those skilledin the art.

[0031] Alternately, the plasma can be formed using electron cyclotronresonance (ECR). In yet another embodiment, the plasma is formed fromthe launching of a Helicon wave. In yet another embodiment, the plasmais formed from a propagating surface wave. Each plasma source describedabove is well known to those skilled in the art.

[0032] Referring now to FIG. 7A, the gas injection system 101 ispresented in greater detail. Gas injection system 101 comprises a gasinjection assembly body 210, a gas inject plate 212, optionally one ormore baffle plates 214 may be installed within gas injection plenum 216,and a pressure sensor 220 coupled to the gas injection plenum 216. Ingeneral, the gas injection assembly body 210, the gas inject plate 212,and the one or more baffle plates 214 can, for example, be fabricatedfrom aluminum, or similar material. However, in order to minimize thedamage sustained by exposure to a processing plasma, a consumable orreplaceable component can be inserted within the processing chamber toprotect the surfaces of more valuable components that would imposegreater costs during frequent replacement. For example, the gasinjection system 101, depicted in FIG. 7A, can further comprise aconsumable component such as gas inject plate 230. The consumable gasinject plate 230 can be fabricated from materials such as silicon,quartz, sapphire, alumina, carbon, silicon carbide, anodized aluminum,aluminum coated with polyimide, aluminum coated with Teflon, and spraycoated aluminum. For example, a spray coating can comprise at least oneof Al₂O₃ and Y₂O₃. In another embodiment, the spray coated layercomprises at least one of a Ill-column element (column III of periodictable) and a Lanthanon element. In another embodiment, the III-columnelement comprises at least one of Yttrium, Scandium, and Lanthanum. Inanother embodiment, the Lanthanon element comprises at least one ofCerium, Dysprosium, and Europium. In another embodiment, the compoundforming the spray coated layer comprises at least one of Yttria (Y₂O₃),Sc₂O₃, Sc₂F₃, YF₃, La₂O₃, CeO₂, Eu₂O₃, and DyO₃. In general, it isdesirable to select surface materials that, during erosion, minimize theintroduction of unwanted contaminants, impurities, etc. to theprocessing plasma and possibly to the devices formed on the substrate.

[0033] The pressure sensor 220 can, for example, be a Type 628B Baratronabsolute capacitance manometer commercially available from MKSInstruments, Inc. (Andover, Mass.). As shown in FIG. 2, gas injectionsystem 101 further comprises one or more mass flow controllers 240 andpressure regulators (or valves) 242 coupled to the gas injectionassembly body 210 in order to supply a process gas or mixture of gasesto the gas injection plenum 216.

[0034] Alternately, as shown in FIG. 7B, gas injection system 101 doesnot include gas inject plate 212, and consumable gas inject plate 230can couple directly to the gas injection assembly body 210.

[0035]FIG. 8A depicts a cross-section of a non-eroded orifice 260extending through gas inject plate 212. FIG. 8B depicts the same orifice260 after it has been eroded during processing. Before processing, theorifice(s) 260 extending through consumable gas inject plate 230 haveyet to be exposed to plasma and, therefore, are not yet eroded. However,after significant processing, the erosion of the consumable gas injectplate 230, particularly proximate the orifice exit(s), affectssubstantial changes to the orifice diameter 262 (cross-section) asdepicted in FIG. 8B. Typically, the orifice diameter 262 at the exit isdrastically enlarged and the orifice length is shortened. For example,an orifice with length 5 mm and diameter 0.5 mm (i.e. aspect ratio of10) formed within a silicon plate can be eroded to the extent shown inFIG. 8B within approximately 250 RF hours.

[0036] Due to the change in orifice length and diameter, the flowconductance C of the orifice(s) 260 changes predominantly in inverseproportion to the length and directly proportional to the diameter tothird power for a free molecular flow and to the fourth power for acontinuum flow. Therefore, during any change in processing pressure ormass flow rate, the response of the pressure P in the gas injectionplenum 216 depends primarily upon the volume of the gas injection plenum216 (fixed) and the net conductance of the orifice(s) 260 in theconsumable gas inject plate 230.

[0037] For example, during vacuum pump-down following wafer exchangewith the transfer system (not shown) and preceding the initiation of aprocess gas flow rate, the vacuum pressure within the processing systemis reduced (possibly to a base pressure) and, subsequently, the gasinjection plenum pressure P is reduced, however, following a delay Δt.FIG. 8C presents an exemplary time trace depicting the response of thepressure P measured using the pressure sensor coupled to the gasinjection plenum 216 during a change in processing pressure. In the casewhere the orifice(s) 260 has eroded (i.e. during an eroded state) andthe flow conductance has subsequently increased, the response time, ordelay, decreases from Δt_(A) to Δt_(B). For instance, with a change inchamber (processing) pressure or mass flow rate, the response time for300-0.5 mm diameter, 10 mm long orifices coupled to a gas injectionplenum with height 25.4 mm and diameter 300 mm is approximately 5seconds. The change in response time, or delay, can be correlated withthe state of the consumable inject plate 230. For example, when the timeresponse, or delay, falls below a pre-determined threshold, then it istime to replace the consumable gas inject plate and an operator isnotified.

[0038] In an alternate embodiment, FIGS. 9A and 9B present a gasinjection system 101 similar in design to that described in FIGS. 7A and7B except that pressure sensor 220 is directly coupled to one or moretest orifices 280. As shown in FIG. 9A, a test conduit 270 is formedwithin an extension 272 of gas inject plate 212 and, optionally, avacuum seal is achieved between an upper surface 274 of extension 272and a lower surface 276 of gas injection assembly body 210 using an(elastomer) O-ring 278. Alternately, as shown in FIG. 9B, a test conduit270 is formed within an extension 290 of gas injection assembly body210.

[0039]FIG. 10 presents a method of determining the lifetime of aconsumable by monitoring the gas injection pressure. For example, theconsumable can comprise the consumable gas inject plate as described inFIGS. 2 through 9B. A procedure 500 begins in step 510 with facilitatinga change in a process parameter. The process parameter comprises atleast one of a processing pressure in the plasma processing chamber ofthe plasma processing device, and a mass flow rate of the process gascoupled to the plasma processing chamber of the plasma processingdevice. The change in the process parameter can be imposed, for example,by: changing the mass flow rate from one processing step to anotherprocessing step, changing the processing pressure from one processingstep to another processing step, initiating a mass flow rate of processgas following the loading of a new substrate, or reducing the processingpressure following the loading of a new substrate and preceding theinitiation of the mass flow rate of process gas.

[0040] In step 520, a response time is determined from a time trace ofthe gas injection pressure measured using the pressure sensor coupled tothe gas injection system, or an nth derivative of the respective timetrace. When the one or more orifices of the consumable gas inject platecorrespond to a non-eroded state, the response time exhibits a firsttime delay Δt_(A) in a first time trace. For example, the consumable gasinject plate has not been eroded when it is either first installed orreplaced, and it has yet to be exposed to an erosive environment, suchas plasma. When the one or more orifices of the consumable gas injectplate correspond to an eroded state, the response time exhibits a secondtime delay Δt_(B) in a second time trace. For example, the consumablegas inject plate has been eroded once it is exposed to an erosiveenvironment, such as plasma, during the processing of one or moresubstrates in the plasma processing device.

[0041] In step 530, the measured response time is compared to the firsttime delay to determine the state of the consumable gas inject plate ofthe gas injection system. In general, if one or more orifices of theconsumable gas inject plate erode, the measured response time is lessthan the first time delay. In one embodiment, the state of theconsumable gas inject plate comprises a partially eroded state when themeasured response time ranges from 25% to 75% of the first time delay.For example, a partially eroded state can require notification of anoperator and a recommendation for replacement of the consumable gasinject plate. In another embodiment, the state of the consumable gasinject plate comprises a fully eroded state when the measured responsetime is less than 25% of the first time delay. (This lower threshold canbe considered as a second delay time against which the measured responsetime can be compared.) For example, a fully eroded state can requireimmediate notification of an operator and replacement of the consumablegas inject plate.

[0042] In an alternate embodiment, a first response time can be measuredfor a first location on the consumable gas inject plate, and a secondresponse time can be measured for a second location on the consumablegas inject plate. For example, the first location can comprise at leastone orifice proximate the center of the consumable gas inject plate, andthe second location can comprise at least one orifice proximate the edgeof the consumable gas inject plate. The first and second measuredresponse times can be utilized to determine a uniformity of the processfor each substrate processed. The resultant uniformity can be monitoredfrom run-to-run, or batch-to-batch, to ensure that the process isperformed within acceptable ranges. When a deviation in the processuniformity exceeds a pre-determined threshold, the operator can benotified for system maintenance.

[0043] Although only certain exemplary embodiments of this inventionhave been described in detail above, those skilled in the art willreadily appreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention.

What is claimed is:
 1. A gas injection system in a plasma processingdevice comprising: a gas injection assembly body configured to receive aprocess gas from at least one mass flow controller; a consumable gasinject plate coupled to said gas injection assembly body, saidconsumable gas inject plate comprising at least one orifice todistribute said process gas to said plasma processing device; a pressuresensor coupled to said gas injection assembly body and configured tomeasure a gas injection pressure within a gas injection plenum formed bysaid gas injection assembly body and said consumable gas inject plate;and a controller coupled to said pressure sensor and configured todetermine a state of said consumable gas inject plate from a change insaid gas injection pressure.
 2. The gas injection system recited inclaim 1, further comprising a gas inject plate between said gasinjection assembly body and said consumable gas inject plate.
 3. The gasinjection system recited in claim 1, wherein said consumable gas injectplate comprises one of silicon, carbon, silicon carbide, quartz,alumina, and coated metal.
 4. The gas injection system as recited inclaim 1, wherein said change in said gas injection pressure results fromat least one of a change in a processing pressure in said plasmaprocessing device and a change in a mass flow rate of said process gas.5. The gas injection system as recited in claim 1, wherein saidcontroller determines a response time for the change in said gasinjection pressure and compares the response time with a first timedelay in a first time trace corresponding to when said at least oneorifice of said consumable gas inject plate corresponds to a non-erodedstate.
 6. The gas injection system as recited in claim 1, wherein saidcontroller determines a response time for the change in said gasinjection pressure and compares the response time with a second timedelay in a second time trace when said at least one orifice of saidconsumable gas inject plate corresponds to an eroded state.
 7. The gasinjection system as recited in claim 6, wherein said second time delayis less than a time delay corresponding to when said at least oneorifice of said consumable gas inject plate corresponds to an erodedstate.
 8. The gas injection system as recited in claim 6, wherein saidstate of said consumable gas inject plate is determined by a comparisonof said response time to said first time delay.
 9. The gas injectionsystem as recited in claim 6, wherein said state of said consumable gasinject plate comprises a partially eroded state when said second timedelay ranges from 25% to 75% of a first time delay corresponding to whensaid at least one orifice of said consumable gas inject platecorresponds to an non-eroded state.
 10. The gas injection system asrecited in claim 6, wherein said state of said consumable gas injectplate comprises a fully eroded state when said second time delay is lessthan 25% of a first time delay corresponding to when said at least oneorifice of said consumable gas inject plate corresponds to an erodedstate.
 11. A plasma processing device comprising: a plasma processingchamber; a gas injection system coupled to said plasma processingchamber, said gas injection system comprising a gas injection assemblybody configured to receive a process gas from at least one mass flowcontroller; and a consumable gas inject plate coupled to said gasinjection assembly body, said consumable gas inject plate comprising atleast one orifice to distribute said process gas to said plasmaprocessing chamber; a diagnostic system, said diagnostic systemcomprising a pressure sensor coupled to said gas injection assembly bodyand configured to measure a gas injection pressure within a gasinjection plenum formed by said gas injection assembly body and saidconsumable gas inject plate; and a controller coupled to said pressuresensor and configured to determine a state of said consumable gas injectplate from a change in said gas injection pressure.
 12. The plasmaprocessing device recited in claim 11, further comprising a gas injectplate between said gas injection assembly body and said consumable gasinject plate.
 13. The plasma processing device recited in claim 11,wherein said consumable gas inject plate comprises one of silicon,carbon, silicon carbide, quartz, and coated metal.
 14. The plasmaprocessing device as recited in claim 11, wherein said change in saidgas injection pressure results from at least one of a change in aprocessing pressure in said plasma processing chamber and a mass flowrate of said process gas.
 15. The plasma processing device as recited inclaim 11, wherein said controller determines a response time for thechange in said gas injection pressure and compares the response timewith a first time delay in a first time trace corresponding to when saidat least one orifice of said consumable gas inject plate corresponds toa non-eroded state.
 16. The plasma processing device as recited in claim11, wherein said controller determines a response time for the change insaid gas injection pressure and compares the response time with a secondtime delay in a second time trace when said at least one orifice of saidconsumable gas inject plate corresponds to an eroded state.
 17. Theplasma processing device as recited in claim 16, wherein said secondtime delay is less than a time delay corresponding to when said at leastone orifice of said consumable gas inject plate corresponds to an erodedstate.
 18. The plasma processing device as recited in claim 16, whereinsaid state of said consumable gas inject plate is determined by acomparison of said response time to said first time delay.
 19. Theplasma processing device as recited in claim 16, wherein said state ofsaid consumable gas inject plate comprises a partially eroded state whensaid second time delay ranges from 25% to 75% of a first time delaycorresponding to when said at least one orifice of said consumable gasinject plate corresponds to an non-eroded state.
 20. The plasmaprocessing device as recited in claim 16, wherein said state of saidconsumable gas inject plate comprises a fully eroded state when saidsecond time delay is less than 25% of a first time delay correspondingto when said at least one orifice of said consumable gas inject platecorresponds to an non-eroded state.
 21. A method of determining thestate of a gas injection system in a plasma processing devicecomprising: changing a process parameter in said plasma processingdevice to affect a change of a gas injection pressure in said gasinjection system, said gas injection system comprising a gas injectionassembly body configured to receive a process gas from at least one massflow controller, a consumable gas inject plate coupled to said gasinjection assembly body, said consumable gas inject plate comprising atleast one orifice to distribute said process gas to said plasmaprocessing device, a pressure sensor coupled to said gas injectionsystem, and a controller coupled to said pressure sensor; measuring aresponse time corresponding to a change of said gas injection pressureusing said pressure sensor, wherein said response time corresponds to afirst time delay when said consumable gas inject plate exhibits anon-eroded state and said response time corresponds to a second timedelay when said consumable gas inject plate exhibits an eroded state;and comparing said response time with said first time delay in order todetermine said state of said gas injection system.
 22. The methodrecited in claim 21, further comprising a gas inject plate between saidgas injection assembly body and said consumable gas inject plate. 23.The method recited in claim 21, wherein said consumable gas inject platecomprises one of silicon, carbon, silicon carbide, quartz, alumina, andcoated metal.
 24. The method as recited in claim 21, wherein saidprocess parameter comprises at least one of a processing pressure insaid plasma processing device and a mass flow rate of said process gas.25. The method as recited in claim 21, wherein said first time delay isgreater than said second time delay.
 26. The method as recited in claim21, wherein said state of said consumable gas inject plate is determinedby a comparison of said response time to a fraction of said first timedelay.
 27. The gas injection system as recited in claim 21, wherein saidstate of said gas injection system comprises a partially eroded statewhen said response time ranges from 25% to 75% of said first time delay.28. The gas injection system as recited in claim 21, wherein said stateof said gas injection system comprises a fully eroded state when saidresponse time is less than 25% of said first time delay.